1. Field
One or more aspects of embodiments of the present disclosure relate to a positive active material, a positive electrode and a lithium battery including the positive active material, and a method of manufacturing the positive active material.
2. Description of the Related Art
With the development of small high-tech devices such as digital cameras, mobile devices, laptops, and computers, the demand for a lithium secondary battery as an energy source has rapidly increased. In addition, with the spread of hybrid and plug-in electric vehicles (e.g., hybrid electric vehicle or HEV, plug-in hybrid electric vehicle or PHEV, and electric vehicle or EV) by the name of xEV, the development of a safe lithium-ion battery of high capacity is ongoing.
In order to realize a lithium battery consistent with the purposes described above, a variety of positive active materials are being considered.
As the positive active material for the lithium-ion battery, a single-component lithium cobalt oxide (LiCoO2) has been mainly used, but alternatively, there is a current trend of using a high-capacity, layered lithium composite metal oxide (e.g., Li(Ni—Co—Mn)O2, Li(Ni—Co—Al)O2, etc). In addition, a highly safe spinel-type lithium manganese oxide (LiMn2O4) and an olivine-type lithium iron phosphate (LiFePO4) have also attracted attention.
During charge and discharge cycles of a lithium battery, a variety of coating layers may be formed to suppress (or reduce) a reaction between the positive active material and an electrolyte solution so as to improve lifetime of the lithium battery.
According to the related art, the coating material for the positive active material is mostly a metal oxide, which blocks a direct reaction with the electrolyte solution during the charge and discharge cycles so as to improve a lifetime of the positive active material. However, such a coating material is electrically inactive, and thus, as the positive active material is coated with more of the coating material, the capacity and rate property (i.e., charge and discharge rates) of the positive active material decrease. Accordingly, the lithium ion battery including the positive active material may have a structure in which the intercalation and deintercalation of lithium ions is difficult.
Therefore, in comparison with the coating material of the related arts, the development of new coating materials having no degradation in rate property or having a very low rate property in addition to improved lifetime properties is beneficial.